Telecommunications equipment, particularly communications equipment, is equipped with temperature-stabilized oscillator circuits for the purpose of forming high-precision alternating signals, particularly clock signals. The oscillator circuits are mainly realized by voltage-controlled oscillator circuits that form part of a phase-locked loop. With the assistance of these phase-locked loops, the clock signals formed in the communication systems are controlled synchronously with respect to their phase to a reference clock signal supplied to the communications system, for example, from a higher-ranking clock means. The phase-locked loop is mainly formed by an oscillator circuit and by a means that further-processes the clock signals. The control signals for controlling the heating elements are usually formed in these further-processing means, for example, a microprocessor system equipped with appropriate programs, and are communicated to a separate input of the oscillator circuit for controlling the heating elements. The measurement of the current temperature in an oscillator circuit is thereby effected either via a temperature sensor element, for example a semiconductor temperature sensor, or by a temperature-measuring oscillator. A temperature-measuring oscillator is realized such that optimally large frequency changes of the formed clock signals are produced for temperature changes. These temperature sensor signals or measuring oscillator signals are evaluated in the further-processing means and the current temperature of the oscillator circuit is calculated. Dependent on the result of the temperature measurement, the heating element in the oscillator circuit is subsequently activated via separate connections or is switched off in such a way that the temperature of the oscillator circuit remains largely constant.